. >> let's get back to medicare. >> reporter: and it didn't take long for the deep philosophical disagreements to come through. first on taxes. >> now, governor romney's proposal that he's been promoting for 18 months calls for a $5 trillion tax cut on top of $2 trillion of additional spending for our military. and he is saying that he is going to pay for by closing loopholes and deductions. the problem is he's been asked over 100 times how you would close those deductions and loopholes and he hasn't been able to identify them. >> virtually everything he said about my tax plan is inaccurate. if the tax plan he described, i would say absolutely not. i'm not looking for a $5 trillion tax cut. what i've said is i won't put in place a tax cut that adds to the deficit. >> for 18 months he's been running on this tax plan. and now, five weeks before the election, he's saying that his big bold idea is never mind. >> let me repeat what i said. i'm not in favor of a $5 trillion tax cut, that's not my plan. >> reporter: another stark difference, medicare, one of the few times the president played aggress